This invention relates to fine, uniform longitudinal compressive treatment of webs and web-form materials for changing their physical properties--treatments, for example, to provide shrink-resistance, stretchiness, increased density, softness, texture, improved filtering action, and other properties to textile and textile-like, including non-woven, web materials. Reference is made to prior art such as U.S. Pat. to Cluett No. 1,861,424; Wrigley et al. NO. 2,263,712; Barnard No. 2,958,608; Cohn et al. Nos. 3,015,145 and 3,015,146; Harmon No. 3,059,313 and the present inventor Walton Nos. 2,765,513; 2,765,514; 2,915,109; 3,260,778; 3,426,405; 3,810,280; 2,869,768; and 3,975,806.
Prior machines have been successful for many webs and end uses, but have still presented serious deficiencies in other important applications, producing, for example, unwanted differences in the two sides of a web being treated, or shear across the thickness of the material, or crushing of the material in the direction of the web thickness.
In the case of shrink-proofing tubular knit dyed goods using available machines, physical differences in the two sides, hence differences in the apparent color of the two sides, cause matching problems if apparel are made with the treated goods.
In the case of compressively treating loosely bound bats of filter fibers using available machines, unwanted crushing in the direction of the web thickness can detrimentally affect physical properties and the filtering action of the final product.
Prior machines have also presented problems in initial alignment of machine parts, in maintaining uniform settings throughout long production runs, and in the frequent need to replace parts subject to wear.
Many of the deficiencies of prior machines noted above are traceable to the manner in which the drive forces are applied to the web to be treated. In commercially successful machines the drive often involves a single roll and a stationary shoe which presses the web against the roll. While this is successful in providing drive force, it does so only while also providing certain shear and crushing forces. As has long been realized, if a machine could be provided for present purposes employing a pair of drive rolls forming a driving nip for the web, these deficiencies could be avoided or eliminated. The problem of doing this, however, is not simple because the kind of treatment being sought is one of extreme fineness, to be applied very uniformly over the web, without producing destructive action, lint, or unwanted folds or crepes. At the same time, the geometry provided by a pair of rolls is very limiting in respect to the space and manner of insertion of retarding members. With certain prior arrangements, it has been found that retarding blades and the like cut the material, or the material goes beneath the edge of the blade and becomes snagged. In other cases, the retarding members do not apply sufficient force to provide the fine, dense treatment desired, or spurting and uneven treatment, or detrimental gross folds or uwanted superficial crepe occur.